Steganography techniques exploit these redundant bits to hide the information/payload by altering them in such a way that alterations cannot be detected easily by humans or computers. Images are an excellent medium for concealing information because they provide a high degree of redundancy - which means that there are lots of bits that are there to provide accuracy far greater than necessary for the object's use (or display). There are a bunch of techniques for each of them but this article aims to provide an exhaustive overview of Image Steganography. Today steganography is mostly used on computers with digital data, like Image, Audio, Video, Network packets, etc, acting as the carriers. Hence a hybrid approach where we encrypt the message and then hide its presence amplifies the security. Both cryptography and steganography, protect the information in their own way but neither alone is perfect and can be compromised. Sometimes, it becomes necessary to not only hide the meaning of the message but also hide its existence, and the field that deals with this is called Steganography. The techniques of cryptography try to ensure that it becomes extremely difficult to extract the true meaning of the message when it goes into the wrong hands. This lead to the development of the field of Cryptography that deals with hiding the meaning of a message. Since the rise of the Internet, making communication more secure has been a priority. The left half of the image below is a bunch of microdots, sent by German spies and intercepted by Allied intelligence, and the right half is the camera that was used to print such microdots. Most of these early developments happened during World War I and II where everyone was trying to outsmart each other. Invisible inks, microdots, writing behind postal stamps are all examples of steganography in its physical form. Steganography continued over time to develop into new levels. In modern times, steganography can be looked into as the study of the art and science of communicating in a way that hides the presence of the communication. The word is derived from the Greek word “στεγαυω” which means "secret or covered writing". This art of concealing message is called Steganography. After his hair grew back the slave left for Miletus and upon his arrival, his head was shaved again and the message was revealed which told Aristagoras to revolt against the Persians and start the Ionian revolt. The text that was tattooed was a secret message that Histiaeus wanted to send to his son-in-law Aristagoras in Miletus. Would you shave your head and get it tattooed? Probably no, but a slave in ancient Greece was made to do so in the 440 BCE by a ruler named Histiaeus.
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